Desiccant composition containing surface-modified powders of metal oxides useful for manufacture and protection of moisture-sensitive devices

Abstract

A desiccant composition is described. The desiccant composition has a polymeric binder and a dispersion of powders of hygroscopic inorganic oxides as desiccant materials, in which the desiccant powders are finely dispersed in consequence of their surface-modification by fatty acid anions without affecting their moisture sorption performances.

The invention claimed is: 
     
       1. A desiccant composition consisting of:
 particles of at least one first hygroscopic inorganic oxide and a polymeric binder, said particles of at least one first hygroscopic inorganic oxide having an external surface and being selected in the group consisting of alkali metal oxides, alkaline-earth metal oxides, manganese oxide and zinc oxides, 
 wherein 
 said particles of at least one first hygroscopic inorganic oxide have dimensions in the range of from 0.05 μm to 20 μm and are functionalized at said external surface by anions of general formula C n H 2n+1 COO − , wherein n is an integer number greater than 11. 
 
     
     
       2. The desiccant composition according to  claim 1 , wherein n is between 13 and 23. 
     
     
       3. The desiccant composition according to  claim 2 , wherein said anions of general formula C n H 2n+1 COO −  are selected in the group consisting of tetradecanoate, hexadecanoate, octadecanoate, icosanoate, docosanoate, tetracosanoate. 
     
     
       4. The desiccant composition according to  claim 1 , wherein said first hygroscopic inorganic oxide is selected in the group consisting of lithium, magnesium, calcium, strontium and barium oxides. 
     
     
       5. The desiccant composition according to  claim 1 , wherein the particles of said first hygroscopic inorganic oxide are in amount of between 5% and 50% by weight with respect to the total composition weight. 
     
     
       6. The desiccant composition according to  claim 1 , wherein the molar ratio of said anions of general formula C n H 2n+1 COO −  with respect to said first hygroscopic inorganic oxide is higher than 1:100. 
     
     
       7. A desiccant composition consisting of:
 particles of at least one first hygroscopic inorganic oxide and a polymeric binder, said particles of at least one first hygroscopic inorganic oxide having an external surface and being selected in the group consisting of alkali metal oxides, alkaline-earth metal oxides, manganese oxide and zinc oxides, 
 wherein 
 said particles of at least one first hygroscopic inorganic oxide have dimensions in the range of from 0.05 μm to 20 μm and are functionalized at said external surface by anions of general formula C n H 2n+1 COO − , wherein n is an integer number greater than 11, and 
 a second hygroscopic inorganic oxide. 
 
     
     
       8. The desiccant composition according to  claim 7 , wherein said second hygroscopic inorganic oxide is selected among lithium oxide and magnesium oxide. 
     
     
       9. The desiccant composition according to  claim 7 , wherein the weight concentration of said second hygroscopic inorganic oxide is comprised between 10 and 50 w/w % respect to the total hygroscopic inorganic oxide content. 
     
     
       10. The desiccant composition according to  claim 1 , wherein said polymeric binder is selected in the group consisting of epoxy resins, epoxyacrylic resins, acrylic resins, polyurethane resins and siloxane matrices. 
     
     
       11. A moisture-sensitive device containing a desiccant body or film comprising the desiccant composition according to  claim 1 . 
     
     
       12. The moisture-sensitive device according to  claim 11 , wherein said moisture-sensitive device is selected in the group consisting of microelectromechanical devices, micro-opto-electromechanical devices, opto-electronic devices for telecommunication applications, medical implantable devices, organic solar cells and organic electronic devices. 
     
     
       13. The desiccant composition according to  claim 1 , wherein said particles of at least one first hygroscopic inorganic oxide have dimensions in the range from 0.1 to 10 μm. 
     
     
       14. The desiccant composition according to  claim 1 , wherein the particles of said first hygroscopic inorganic oxide are in amount of between 30% and 50% by weight with respect to the total composition weight. 
     
     
       15. The desiccant composition according to  claim 1 , wherein the anion of general formula C n H 2n+1 COO −  is comprised in a corresponding carboxylate salt of a metal selected in the group consisting of alkali metals, alkaline-earth metals, manganese and zinc. 
     
     
       16. The desiccant composition according to  claim 7 , wherein the second hygroscopic inorganic oxide is not functionalized by the anions of general formula C n H 2n+1 COO − . 
     
     
       17. The desiccant composition according to  claim 16 , wherein the second hygroscopic inorganic oxide has a lower molecular weight and lower surface area than the first hygroscopic inorganic oxide. 
     
     
       18. The desiccant composition according to  claim 1 , wherein the desiccant composition has a sorption capacity of at least 25% by weight. 
     
     
       19. The desiccant composition according to  claim 7 , wherein the desiccant composition has a sorption speed of 2.0 mg cm −2  min −1  at 22° C. and 55% relative humidity.